Function addUser

run/websockets/users.js:19–24

(id, name, room)

// Record socket ID with user's name and chat room
function addUser(id, name, room) {
  if (!name && !room) return new Error('Username and room are required');
  if (!name) return new Error('Username is required');
  if (!room) return new Error('Room is required');
  users.set(id, {user: name, room});
}

// Return user's name and chat room from socket ID
function getUser(id) {